# Math Help - Probability function P(X=k)

1. ## Probability function P(X=k)

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2. Originally Posted by totalnewbie
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Attempting to cut to the chase, what it looks like you're trying to do is find the mean and variance of a geometric distribution.

$E(X) = \sum_{k = 1}^{k = \infty} k p q^{k-1}$.

It's a routine calculation, found in many statistics textbooks. I can't be bothered typing out a solution .... That's why google exists.

Edit: This thread has some relevance: http://www.mathhelpforum.com/math-he...ee-proofs.html